Composite ventilation tube

ABSTRACT

A medical ventilation tube for placement in an opening formed in an anatomical structure, such as the tympanic membrane of the ear, includes a hollow tubular shaft made of a first material having a hardness or durometer to maintain a passage through the shaft when the medical ventilation tube is placed in the opening, and a flange made of a second material having a hardness or durometer less than that of the first material to permit the flange to deform in response to contact with the anatomical structure during removal of the medical ventilation tube from the opening.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to medical ventilationtubes and, more particularly, to myringotomy ventilation tubes that canbe placed in the tympanic membrane of the ear to drain fluid andalleviate a buildup or reduction of pressure in the middle ear.

[0003] 2. Description of the Prior Art

[0004] The installation of tubes in the tympanic membrane, whichseparates the middle ear from the outer ear, is a well-known remedy fortreating inflammation of the middle ear or otitis media. Typically, amyringotomy is performed to create an opening in the tympanic membraneand a vent or drain in the form of a tube is inserted into the openingto permit drainage of fluid from the middle ear to alleviate a buildupor reduction of pressure in the middle ear cavity. The tube functions tomaintain the opening in the tympanic membrane for a sufficient period oftime following the surgery to allow pressure to equalize between themiddle and outer ears. Frequently, the condition of buildup or reductionof pressure in the middle ear cavity which the tube is intended toalleviate requires that the tube remain in place for a significantperiod of time ranging in duration from about six to about twenty fourmonths.

[0005] A variety of ventilation tubes for insertion into an opening inthe tympanic membrane have been introduced over the years. Prior artventilation tubes without flanges at either end are easy to insert intothe myringotomy opening but are disadvantageous in that they can beaccidentally extracted from the tympanic membrane. On the other hand,ventilation tubes having flanges at one or both ends are less likely tobe accidentally extracted from the tympanic membrane but are difficultto insert into and extract from the myringotomy openings, tending toenlarge the myringotomy openings such that the tendency of the tubes tofall out of the membrane increases. Attempts to fabricate prior artventilation tubes of softer materials help alleviate problems associatedwith insertion and removal of the tubes through openings in the tympanicmembrane but contribute to problems related to bending or buckling ofthe tubes during insertion while detracting from the ability of the tubeto maintain an opening in the tympanic membrane.

SUMMARY OF THE INVENTION

[0006] Accordingly, it is a primary object of the present invention toovercome the disadvantages of the prior art and to improve ventilationtubes of the type used in maintaining an opening in anatomicalstructures such as the tympanic membrane.

[0007] It is another, more specific, object of the present invention toease insertion of a ventilation tube into an opening in an anatomicalstructure while preventing inadvertent extrusion and facilitatingremoval.

[0008] Yet another object of the present invention is to preventenlargement of an opening in an anatomical structure, such as thetympanic membrane, in response to insertion or removal of a medicalventilation tube through the opening.

[0009] Still another object of the present invention is to form aventilation tube as a composite structure made of two or more materialsof different durometer.

[0010] It is a further object of the present invention to maintain anopening in an anatomical structure by use of a ventilation tube having ahollow shaft made of a rigid or hard material and a flange formed at adistal end of the shaft made of a softer, more flexible material.

[0011] The present invention is generally characterized in a medicalventilation tube for placement in an anatomical structure including ahollow tubular shaft having a passage formed therethrough, the hollowtubular shaft being made of a first material having a rigidity to resistbending and maintain the passage in an open condition when theventilation tube is placed in the anatomical structure, and a flangeextending outwardly from the hollow tubular shaft, the flange being madeof a second material having a rigidity less than that of the firstmaterial to permit the flange to deform in response to contact with theanatomical structure. The first material is preferably a polymer havinga durometer no greater than about 100 on the Shore A hardness scale, andthe second material is also preferably a polymer having a durometer lessthan that of the first material but greater than about 20 on the Shore Ahardness scale. In a most preferred embodiment, the first material is apolymer having a durometer of about 90 to about 95 on the Shore Ahardness scale and a second material is a polymer having a durometer ofabout 50 on the Shore A hardness scale.

[0012] Another aspect of the present invention is generallycharacterized in a method of making a medical ventilation tube includingthe steps of forming a hollow tubular shaft from a first material havinga rigidity to resist bending and to maintain a passage through the shaftwhen the ventilation tube is placed in an anatomical structure, andmolding a flange onto the hollow tubular shaft using a second materialhaving a rigidity less than that of the first material to permit theflange to be deformed in response to contact with the anatomicalstructure.

[0013] Some of the advantages of the present invention are that theventilation tube can be inserted into an opening in an anatomicalstructure, such as the tympanic membrane, without buckling or bending ofthe hollow shaft, that extrusion of the ventilation tube is preventedwhile maintaining a passage of substantially constant diameter throughthe opening, and that the ventilation tube can be formed using a widerange of materials having a variety of properties suitable for improvingease of insertion and removal, preventing extrusion and maintainingstructural rigidity of the ventilation tube.

[0014] Other objects and advantages of the present invention will becomeapparent from the following description of the preferred embodimentstaken in conjunction with the accompanying drawings, wherein like partsin each of the several figures are identified by the same referencecharacters.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a top plan view, partly in section, showing aventilation tube according to the present invention.

[0016]FIG. 2 is a fragmentary side view of the ventilation tube of FIG.1.

[0017]FIG. 3 is a front elevational view of the ventilation tube of FIG.1.

[0018]FIG. 4 is a fragmentary side view, in section, taken through line4-4 in FIG. 1.

[0019]FIG. 5 is an exploded perspective view of a mold used infabricating a ventilation tube according to the present invention.

[0020] FIGS. 6-10 are fragmentary sectional side views illustrating amethod of making a ventilation tube according to the present invention.

[0021]FIG. 11 is a perspective view, partly in section, illustrating useof a ventilation tube according to the present invention.

[0022]FIG. 12 is a fragmentary side view, partly in section, showing amodification of the ventilation tube according to the present invention.

[0023]FIG. 13 is a fragmentary side view, partly in section, showinganother modification of the ventilation tube according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The medical ventilation tube of the present invention can be usedto maintain an opening in any anatomical structure within the body; and,accordingly, while the ventilation tube is described herein as amyringotomy ventilation tube for placement in an opening formed in thetympanic membrane of the ear, it will be appreciated that the medicalventilation tube of the present invention can be placed in othernaturally occurring and surgically created openings throughout the body.

[0025] A ventilation tube 10 according to the present invention, asshown in FIGS. 1-4, includes a hollow tubular body or shaft 12 and aflanged end portion 14. Shaft 12 is formed of a right circular cylinder16 with a proximal end 18, a distal end 20 and a lumen 22 extendingbetween the proximal and distal ends to define at least part of apassage through an anatomical structure such as the tympanic membrane ofthe ear. Shaft 12 is preferably made of a medically acceptable plasticor metal material having a hardness or durometer suitable forwithstanding axial insertion forces without buckling or bending and formaintaining the passage in a substantially unobstructed, open conditionto permit drainage and ventilation of the middle ear over extendedperiods of time.

[0026] End portion 14 includes a cylindrical section 24 extending fromthe distal end of shaft 12 to a transverse cross-member or flange 26. Asbest seen in FIG. 2, flange 26 is generally semi-cylindrical incross-section with a concave side 28 facing distally and a convex side30 facing proximally to form an abutment surface for contacting thetympanic membrane of the ear around the myringotomy opening. A pair ofsemi-circular cut-outs or notches 32 and 34 are formed along distaledges 36 and 38 of the flange in opposed relation near the center of theflange to permit bending of the flange from the transverse positionshown in FIG. 1 to a collapsed position facilitating removal of theventilation tube from the tympanic membrane without enlargement of themyringotomy opening. In the collapsed position, opposed ends or ears 40and 42 of the flange are pivoted about notches 32 and 34 into matingcontact along a longitudinal axis of the ventilation tube where theycooperate to form a tubular extension similar in diameter to shaft 12.Cylindrical section 24 and flange 26 are preferably formed as anintegral one-piece construction using a medically acceptable metal orplastic material having a hardness or durometer less than that of theshaft to facilitate bending of the flange during insertion and removalof the ventilation tube so as to minimize trauma to the tympanicmembrane.

[0027] In a preferred embodiment, shaft 12 and flanged end portion 14are formed of a polymeric material known as C-Flex thermoplasticelastomer. The basic formula of the C-Flex material is described in U.S.Pat. Nos. 4,386,179 and 4,613,640, the disclosures of which areincorporated herein by reference. Briefly, the base component of theC-Flex material is a Styrene-Ethylene/Butylene-Styrene block copolymer(SEBS). Other components, such as silicone oil, mineral oils, andpolypropylene can be added in varying ratios to obtain a desireddurometer. “Durometer,” as used herein, refers to the hardness of apolymer measured using the Shore A, one second scale for plastics orASTM Method 2240. From a practical standpoint, the durometer of theshaft and flanged end portion of the ventilation tube can vary withinthe range of about 20 to about 100, so long as a durometer differentialis maintained whereby the shaft material is of higher durometer than theflange material. Shaft 12 is preferably formed of a C-Flex polymer orsimilar material having a durometer of about 90 to about 95. End portion14 is preferably formed of a C-Flex polymer or similar material having adurometer of about 45 to about 55. Examples of other polymeric materialsthat can be used include Teflon, Silicone and PTFE. An advantage offorming the shaft and flanged end portion of similar materials, such asthe C-Flex polymers, is that they can be readily fused or bondedtogether to form a secure attachment that will not separate duringnormal implantation and removal procedures.

[0028] The ventilation tube 10 described thus far resembles in size andshape a conventional ventilation tube of the type sometimes referred toas a “Goode T-Tube.” It will be appreciated, however, that the shaft andflanged end portion of the present invention can be configured innumerous other ways to resemble any type of ventilation and drain tubehaving a tubular shaft and a flange at one or both ends of the shaft.For example, the ventilation tube of the present invention couldresemble in size and shape Touma T-Type, Donaldson, Armstrong, Pope,Collar Button, Per-Lee or Baldwin Butterfly type ventilation tubes.

[0029] The shaft 12 and end portion 14 of the ventilation tube 10 can befabricated using any suitable manufacturing process and can be securedto one another by thermal or adhesive bonding or by mechanicalattachment. A preferred manner of forming the medical ventilation tube10 is by molding the flanged end portion 14 with the shaft 12 positionedin the mold such that the flanged end portion is formed simultaneouslywith attachment of the shaft. As shown in FIGS. 5 and 6, the mold hastwo parts 44 and 46. Mold part 44 has two semicylindrical recesses 48formed therein in the shape of flanged end part 14; however, any numberof recesses can be formed in mold part 44 depending upon the number ofmedical vent tubes to be made. A through hole 50 extends perpendicularlydownward from the bottom of each recess 48 to a bottom face of the moldpart to define an outer surface of shaft 12.

[0030] Mold part 46 has two semicylindrical projections 52 formedthereon in opposed relation to recesses 48. Projections 52 have a lengthcorresponding to the length of recesses 48 but are of smaller radius tobe radially spaced from inside surfaces of recesses 48 when the moldparts are assembled as shown in FIG. 6. The space between projections 52and recesses 48 correspond in size and shape to flange 26 with theexception of cutouts 34 and 36 which are formed by a second pair ofsemicylindrical projections 54 that extend transversely across thecenter of each projection 52 in opposed relation to a pair of similarlysized semicylindrical recesses 56 formed in mold part 44 across recesses48.

[0031] The inner diameter or lumen 22 of each shaft 12 is defined by acore pin 58 disposed within hole 50. Core pin 58 includes a cylindricalbase 60 snugly fitted within hole 50 and a post 62 of smaller diameterthan the base disposed concentrically within hole 50 between base 60 andprojection 52. Channels 64 a and 64 b connect recesses 48 with a centralopening 66 formed through mold part 46 to accommodate a nozzle or thelike through which a polymeric material can be injected under pressure.

[0032] In forming the medical ventilation tube 10, mold parts 44 and 46are assembled as shown in FIG. 6 and held together by use of clamps,threaded bolts or any other conventional means to prevent separation ofthe mold parts when polymeric material is injected into the mold underpressure. In the assembled condition, the projections on mold part 46fit within the recesses in mold part 44 to define cavities having theshape of flanged end portion 14, and core pins 58 fit within holes 50 todefine cavities having the shape of shaft 12.

[0033] Referring now to FIG. 7, a first polymeric material 67 ofrelatively high durometer, such as a 90 to 95 durometer C-Flex material,is injected into the mold and cured in accordance with the materialmanufacturer's recommendations to produce a molded part of relativelyhigh durometer resembling the medical vent tube. The material isinjected into the mold through opening 66 in mold part 46 and isdirected by channels 64 a and 64 b into the space between projections 52and recesses 48 to form a flanged end portion and between core pin 58and hole 50 to form the shaft.

[0034] Once the high durometer material has cured, mold parts 44 and 46are pulled apart and core pins 58 are punched through mold part 44 asshown in FIG. 8 to eject the molded parts. End portion 14′ of eachmolded part is separated from the shaft, for example by cutting acrossthe broken line shown in FIG. 8, and the separated end portion 14′ isdiscarded. Shaft 12 of the molded part is retained so that it can beplaced over core pin 58 and positioned within the mold as shown in FIG.9 when flanged end portion 14 of the medical vent tubes is to be formed.Since shaft 12 essentially fills the space between core pin 58 and hole50, when a second polymeric material 69 of lower durometer than thefirst, such as a 45 to 55 durometer C-Flex material, is injected intothe mold, only the cavity having the shape of the flanged end portionwill be filled with the low durometer material. As a consequence ofmolding the flanged ends portion 14 with the shaft 12 positioned in themold, the flanged end portion will thermally bond with the shaft to formthe medical ventilation tube 10 as shown in FIG. 10. When the lowdurometer material has cured, mold parts 44 and 46 are pulled apart andcore pins 58 are punched through the mold part 44 as describedpreviously to eject the medical ventilation tubes 10 from the mold.

[0035] The manufacturing process described above is exemplary of thetypes of processes that can be used in forming the medical ventilationtube 10; however, the shaft 12 and end portion 14 of the ventilationtube 10 can be fabricated using any suitable manufacturing process andcan be secured to one another using any suitable means of attachment.For example, shaft 12 could be formed using other well knownmanufacturing methods, such as by extruding a continuous length ofhollow tubing and cutting the hollow tubing to a predetermined lengthcorresponding to the length of the shaft. Also, shaft 12 could be madeof a metal material, such as stainless steel, and provided withundercuts, grooves or other structural features to facilitate mechanicalattachment and retention of the molded end portion 14.

[0036] In use, the ventilation tube 10 can be placed in a myringotomyopening formed in the tympanic membrane of the ear as illustrated inFIG. 11, to treat persistent middle ear effusion or severe otitis media.The ventilation tube 10 is preferably picked up by means of aconventional forceps grasping the proximal end of shaft 12 and isadvanced into the auditory canal C of the outer ear toward the tympanicmembrane M. Because shaft 12 is formed of a rigid material having arelatively high durometer or hardness, the shaft will resist buckling orbending caused by axial insertion forces, such as those caused bycontact with anatomical structures of the ear. As a result, therelatively soft and flexible end portion 14 can be precisely positionedadjacent the myringotomy opening by manipulation of shaft 12 and, whenthe longitudinal axis of the ventilation tube is substantially alignedwith the opening, the end portion of the ventilation tube can beinserted through the opening. When opposed ends 40 and 42 of the flangepass completely through the opening to be disposed on the opposite,middle ear side of the tympanic membrane, the flange is released andwill recover its original transverse shape to prevent accidentalextraction or extrusion of the ventilation tube from the opening. Theventilation tube is thus implanted in the tympanic membrane of the earwith shaft 12 placed in the myringotomy opening to maintain a passage ofsubstantially constant diameter through the membrane to allowunobstructed drainage and ventilation of the middle ear over brief orextended periods of time. The ventilation tube can be removed by simplygrasping the proximal end of shaft 12 with a forceps and extracting theend portion 14 through the myringotomy opening. As end portion 14 iswithdrawn proximally through the opening, the convex side of flange 26abuts the tympanic membrane such that opposed ends 40 and 42 of theflange are pivoted or forced together in response to the force fromtissue contact. Since opposed ends of the flange are semi-cylindrical incross-section, they cooperate to form a substantially cylindricalprofile when pivoted forward thereby easing withdrawal of theventilation tube from the tympanic membrane without enlarging themyringotomy opening.

[0037] The shaft and flanged end portion of the ventilation tube can beconnected in various ways without compromising strength or performance.For example, in FIG. 12, an alternate connection is shown wherein thedistal end of shaft 12 includes a recess 68 and the cylindrical sectionof end portion 14 includes a shoulder or step 70 joining the cylindricalsection with a reduced diameter portion 72 configured to fit withinrecess 68. Shaft 12 can be made of a high durometer plastic or rigidmetal material and is held in place by use of an appropriate adhesive 74applied to shoulder 70 and/or other parts of the flanged end portion. Informing the alternate connection shown in FIG. 12, flanged end portion14 is preferably stiffened by mounting on a cylindrical mandrel. Afteradhesive 74 is applied, shaft 12 can be pushed onto the stiffened endportion and left in place until the adhesive has cured.

[0038] Another modified connection, shown in FIG. 13, involves forming astep or shoulder 76 at the distal end of shaft 12 and a recess 78 at theproximal end of flanged end portion 14. A reduced diameter portion 80 ofshaft 12 extending from shoulder 76 is configured to fit within recess78 at the proximal end of flanged end portion 14 to serve as a mandrelstiffening the cylindrical section of the flanged end portion. As aresult, the shaft and flanged end portion can be held in place with heatshrink tubing 82 or the like that surrounds the end portion in thevicinity of reduced diameter portion 80 of the shaft thereby compressingthe end portion against the shaft and producing a tight frictionalengagement or bond. Tubing 82 is preferably made of a biocompatiblematerial of relatively thin wall thickness, such as a 0.001-0.002 inchthick Teflon tubing. Pull strength or, in other words, the forcerequired to separate the shaft from the flanged end portion, can beincreased by texturing the external surface of reduced diameter portion80, for example by forming grooves or a cross hatch pattern on thesurface or by sand blasting the surface prior to assembly.

[0039] From the above, it will be appreciated that, by use of a rigid orhard tubular shaft, the ventilation tube of the present invention can beprecisely positioned within an opening formed in an anatomical structureof the body to maintain a passage through the structure over brief orextended periods of time so as to allow unobstructed drainage andventilation through the anatomical structure. Further, by use of arelatively softer flanged end portion, the ventilation tube of thepresent invention can prevent accidental extrusion and allow removalwithout causing significant trauma to the anatomical structure orenlargement of the opening. The ventilation tube can be placed in anyanatomical structure separating two regions in need of pressureequalization, such as the tympanic membrane that separates the middleand outer ears. The ventilation tube can have any configuration to fitthrough an opening in an anatomical structure while preventinginadvertent extrusion, including configurations utilizing T-Type orround flanges and grommet configurations wherein flanges are arranged inspaced relation along the length of the tubular shaft. By “tubular” ismeant having a passage extending between open ends; and, while theventilation tube of the present invention is described herein as havinga tubular shaft of cylindrical configuration, it will be appreciatedthat tubular shafts of any cross-sectional configuration can be used,including elliptical and polygonal cross-sectional configurations.Further, the tubular shaft can be straight, curved or angled dependingupon procedural use; and, when one or more flanges are to be mounted onthe shaft, the flanges can be oriented at any angle relative to alongitudinal axis of the shaft.

[0040] The material specifications and dimensions of the ventilationtube will vary according to the intended use and, as such, it will beappreciated that the particular materials and dimensions listed hereinare merely exemplary and not meant to be limiting.

[0041] Inasmuch as the present invention is subject to many variations,modifications and changes in detail, it is intended that all subjectmatter discussed above or shown in the accompanying drawings beinterpreted as illustrative only and not be taken in a limiting sense.

What is claimed is:
 1. A medical ventilation tube for placement in ananatomical structure comprising a hollow tubular shaft having a passageformed therethrough, said hollow tubular shaft being made of a firstmaterial having a rigidity to resist bending and maintain said passagein an open condition when said ventilation tube is placed in theanatomical structure; and a flange extending outwardly from said hollowtubular shaft, said flange being made of a second material having arigidity less than that of said first material to permit said flange todeform in response to contact with the anatomical structure.
 2. Amedical ventilation tube as recited in claim 1 wherein said firstmaterial is a polymer having a durometer no greater than about 100 onthe Shore A hardness scale and said second material is a polymer havinga durometer less than said first material but greater than about 20 onthe Shore A hardness scale.
 3. A medical ventilation tube as recited inclaim 2 wherein said first material is a polymer having a durometer ofabout 90 to about 95 on the Shore A hardness scale.
 4. A medicalventilation tube as recited in claim 3 wherein said second material is apolymer having a durometer of about 50 on the Shore A hardness scale. 5.A medical ventilation tube as recited in claim 4 wherein said first andsecond materials are block copolymers.
 6. A medical ventilation tube asrecited in claim 5 wherein said first and second materials areStyrene-Ethylene/Butylene-Styrene block copolymers.
 7. A medicalventilation tube as recited in claim 1 wherein said first material is ametal and said second material is a polymer.
 8. A medical ventilationtube as recited in claim 1 wherein said hollow tubular shaft has adistal end and said flange is mounted at said distal end of said hollowtubular shaft.
 9. A medical ventilation tube as recited in claim 8 andfurther comprising a cylindrical section secured to said distal end ofsaid hollow tubular shaft, said cylindrical section and flange being ofintegral one-piece construction.
 10. A medical ventilation tube asrecited in claim 9 wherein said cylindrical section and said hollowtubular shaft have substantially the same outer circumference.
 11. Amedical ventilation tube as recited in claim 10 wherein said cylindricalsection and said hollow tubular shaft abut one another, and whereinabutting portions of said cylindrical section and said hollow tubularshaft are bonded together.
 12. A medical ventilation tube as recited inclaim 11 wherein a portion of said cylindrical section fits within arecess formed in said hollow tubular shaft.
 13. A medical ventilationtube as recited in claim 11 wherein a portion of said hollow tubularshaft fits within a recess formed in said cylindrical section.
 14. Amedical ventilation tube as recited in claim 13 and further comprisingshrink tubing surrounding said cylindrical section.
 15. A method ofmaking a medical ventilation tube comprising the steps of forming ahollow tubular shaft from a first material having a rigidity to resistbending and to maintain a passage through the shaft when the ventilationtube is placed in an anatomical structure; and molding a flange onto thehollow tubular shaft using a second material having a rigidity less thanthat of the first material to permit the flange to deform in response tocontact with the anatomical structure.
 16. A method of making a medicalventilation tube as recited in claim 15 wherein said molding stepincludes placing the hollow tubular shaft within a mold having a cavityconfigured to form the flange.
 17. A method of making a medicalventilation tube as recited in claim 16 wherein said molding stepfurther includes injecting the second material into the mold to fill thecavity and thermally bond with the hollow tubular shaft.
 18. A method ofmaking a medical ventilation tube as recited in claim 15 wherein saidmolding step further includes using a polymer having a durometer ofabout 50 as the second material.
 19. A method of making a medicalventilation tube as recited in claim 15 wherein said step of forming ahollow tubular shaft includes extruding a continuous length of hollowtubing and cutting the hollow tubing to a predetermined length.
 20. Amethod of making a medical ventilation tube as recited in claim 19wherein said step of forming a hollow tubular shaft further includesusing a polymer having a durometer of about 90 to about 95 as the firstmaterial.
 21. A method of making a medical ventilation tube as recitedin claim 15 wherein said step of forming a hollow tubular shaft includesmolding a ventilation tube using the first material and trimming theflange away.